Armenian President Serzh Sarkisian generated shockwaves with his announcement on September 3 that Yerevan is reversing months of work negotiating an Association Agreement with the European Union and will instead work to join the Moscow-led Customs Union of Belarus, Kazakhstan, and Russia.

Armenia -- like fellow former Soviet republics Ukraine, Moldova, and Georgia -- seemed on track to initial the Association Agreement at the EU's Eastern Partnership summit in Vilnius in November after concluding negotiations on the pact just over a month ago. (Belarus and Azerbaijan are also partnership countries but don't have the same European ambitions.)

However, all those countries have come under intense pressure from Moscow not to sign on with the EU, but instead to join the Customs Union, which Russian President Vladimir Putin intends to transform into a Eurasian Union to rival the EU.

Sarkisian's announcement following talks in Moscow with Putin is far from final and Armenia's parliament would have to approve entry into the customs union. Opposition politicians have declared such a move would be unconstitutional and are prepared to resist it politically and through the courts.

Just one day after the president's statement, a social-media-driven demonstration against the Eurasian Customs Union was held in Yerevan and police detained at least nine people.

Bottom Line

But the bottom line for Armenia may be security. The isolated country depends on Russia in its decades-long standoff with Azerbaijan over its breakaway region of Nagorno-Karabakh. In making his announcement, Sarkisian said that since Armenia is a part of the Russia-led Collective Security Treaty Organization (CSTO), it cannot be isolated from "the corresponding economic space."

Charles Tannock, a British member of the European Parliament's Foreign Affairs Committee, has noted that Yerevan has been under "enormous pressure" from Moscow, including in the realm of security.

"I know that this was a subject of heated debate and the Armenian government would have liked to sign [the Association Agreement], but obviously their main concern has to be a security one," he said. "I know that Putin has been to Baku and has offered to sell up-to-date arms to Azerbaijan. So I can see what it is all about -- it is about putting pressure on Yerevan to do Moscow's bidding and, sadly, it succeeded."

Earlier this year, Moscow began delivery of $1 billion in weaponry to Baku, which has stated repeatedly that it would not rule out settling the Karabakh dispute militarily if efforts to reach a negotiated settlement fail.

'Abrupt Change'

Sergei Minasian, deputy head of the Caucasus Institute in Yerevan, agrees that Armenia's security issues -- which are not addressed at all by the Eastern Partnership -- give Moscow "major leverage" over Yerevan.

Hovannes Igitian, the former head of Armenia's delegation to the Parliamentary Assembly of the Council of Europe, told RFE/RL that Sarkisian's statement was an "abrupt change" for the country that is difficult to explain.

"In the morning before Sarkisian's meeting with Putin, senior members of the ruling Republican Party confirmed that European integration was the way for Armenia to proceed," he said. "I don't know what happened afterward -- even they do not know. Only Serzh Sarkisian can say whether there was pressure on him as a person or as president."

WATCH: An aide to Armenian President Serzh Sarkisian says Yerevan is still committed to initialing an EU Association Agreement.

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Naturally, Armenia's decision has focused attention on the other Eastern Partnership countries, and the big prize is Ukraine. When Sarkisian was meeting Putin in Moscow on September 3, Ukrainian President Viktor Yanukovych on the same day urged his country's parliament to quickly adopt the necessary legislation to ensure "success at the Vilnius summit."

Former Ukrainian Prime Minister Anatoliy Kinakh told RFE/RL that Kyiv understood Armenia's unique geopolitical situation and the role it played in Sarkisian's thinking. "I am convinced there are many interests of Armenia in play here, starting from its complex geographic location, its access to the outside world, and ending with the very difficult question of Karabakh," he said. "I am convinced this had an impact on the Armenian president's statement regarding customs union entry."

Georgia has also made rapid progress within the EU's Eastern Partnership. On September 4, Prime Minister Bidzina Ivanishvili shocked journalists in Tbilisi by saying his government was "studying" the Euarsian Customs Union and so far "we have no position."

Foreign Minister Maja Panhikidze immediately clarified Ivanishvili's remark by saying Tbilisi was only observing the customs union in the same way that the EU and the rest of the world is and that "becoming a member is not an option for Georgia."

Tidal Wave Of Reforms

Moldova -- which has its own Transdniester separatist region that is entirely dependent on Moscow and protected by Russian troops -- has also made considerable progress toward an EU Association Agreement under its pro-Western ruling coalition.

However, Socialist lawmaker Igor Dodon -- formerly a leader of the Moldovan Communist Party -- notes that at least half the public opposes the government's pro-EU course, meaning it will be increasingly hard for the ruling alliance to continue, especially under political and economic pressure from Russia.

The Communist Party forms the largest single faction in Moldova's parliament and it opposes EU integration. Communist lawmaker Eduard Musuc told RFE/RL he supported Sarkisian's decision. "I think this decision is the right one," he said. "But I don't know the conditions under which Armenia will join the customs union and, in this case, the conditions are very important."

The difference in "conditions" is also a key factor for the governments in these countries as they make the choice between the EU and the Moscow-led customs union.

An EU Association Agreement and eventual EU membership entail a tidal wave of political and legal reforms that challenge entrenched elites in many ways. It also means making hard decisions to reduce economic and energy dependence on Russia.

On the contrary, joining Russia's customs union carries none of that baggage, as the membership of Belarus and Kazakhstan clearly demonstrates.

U.S. economist Judy Shelton, vice chairwoman of the National Endowment for Democracy, has warned, however, that this should be a red flag to former Soviet states. "Countries should be very suspicious of the fact that Russia is making it so easy to join, with no legal or political reforms and no request that a country concentrate on increasing the rule of law or reducing corruption," she says. "Basically, to say 'come with us, we have no standards, no values' -- that is not a great enticement."

Some politicians in the Eastern Partnership countries have argued the need to resist this temptation.

"Regarding the Armenian statement, I think that those who seek cheap natural gas instead of advanced technologies will live in the 20th century, while all the civilized world will go into the 21st century," said Serhiy Sobolev, a Ukrainian parliament member and deputy head of the opposition Fatherland (Batkivshchyna) faction. "I think the Armenian people will make their choice, when they understand, as the people of Kazakhstan and Belarus have already understood, what Russia pulled them into."

This report is based on reporting from RFE/RL's Armenian, Azerbaijan, Georgian, Moldovan, and Ukrainian services as well as RFE/RL correspondents Charles Recknagel and Rikard Jozwiak

Robert Coalson

Robert Coalson covers Russia, the Balkans, and Eastern Europe. Send story tips to coalsonr@rferl.org